Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 230732
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
332 AM EDT TUE SEP 23 2014

.SYNOPSIS...
AN UPPER LOW WILL BRING INCREASING RAINFALL TO THE AREA TODAY
THROUGH WEDNESDAY...ALONG WITH WELL BELOW NORMAL TEMPERATURES.
RAINFALL CHANCES WILL CONTINUE THROUGH THE WEEK AS A COASTAL
TROUGH LINGERS JUST OFFSHORE. A WARMING AND DRYING TREND IS
EXPECTED DURING THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM TUESDAY...IF THERE WAS ANY DOUBT IN YOUR MIND THAT
SUMMER IS OVER...TODAY SHOULD ERASE IT. CANADIAN HIGH PRESSURE
OVER OH-PA WILL SHOVE A COOL DRY AIRMASS SOUTHWARD INTO THE
CAROLINAS. THE COLD FRONT AT THE LEADING EDGE OF THIS NEW AIRMASS
IS STALLING OUT OVER THE GULF STREAM. AN UPPER LEVEL LOW HAS CUT
OFF ACROSS FAR-WESTERN SOUTH CAROLINA...AND THE CIRCULATION AROUND
THIS FEATURE WILL DRAW A STREAM OF MID-LEVEL MOISTURE BACK OVER
THE FRONT AND ACROSS THE AREA TODAY. WEAK LOW PRESSURE WILL
ATTEMPT TO CLOSE OFF A CENTER ALONG THE FRONT ALONG THE GA/SC
COAST TONIGHT...BUT MODEL CONSENSUS SAYS IT SHOULD REMAIN AN OPEN
WAVE. HOWEVER THE LOWERING PRESSURES HERE WILL CONTRAST QUITE
STRONGLY WITH THE HIGH OFF TO THE NORTH...CREATING HEALTHY
NORTHEAST WINDS THAT WILL INCREASE TONIGHT TO 15-20 MPH INLAND
WITH GUSTS APPROACHING 30 MPH ON THE BEACHES.

LOOK FOR THE DEVELOPMENT OF A LARGE AREA OF RAIN WITH EMBEDDED
CONVECTIVE SHOWERS JUST BEFORE DAYBREAK ACROSS THE COASTAL
WATERS...SPREADING INLAND THIS MORNING. POPS FOR THE COASTAL CITIES
OF WILMINGTON...SOUTHPORT AND MYRTLE BEACH HAVE BEEN INCREASED TO
80-90 PERCENT. FARTHER INLAND WHERE DRY AIR IS QUITE A BIT BETTER
ENTRENCHED MUCH OF THE PRECIPITATION SHOULD EVAPORATE AND POPS ARE
ONLY IN THE 30-50 PERCENT RANGE. THERE SHOULD BE A FAIRLY TIGHT
GRADIENT IN ACTUAL RAINFALL AMOUNTS JUST OFF THE COAST WITH NO MORE
THAN 0.50 INCHES EXPECTED TO FALL ON THE BEACHES...BUT BETTER THAN
ONE INCH PREDICTED JUST 15 OR 20 MILES OFF CAPE FEAR. FARTHER INLAND
FORECAST RAINFALL AMOUNTS ARE MUCH LOWER...A TENTH OF AN INCH OR
LESS ALONG AND WEST OF I-95.

ALL THIS CLOUD COVER AND RAIN SHOULD REALLY KEEP TEMPERATURES DOWN.
THE PATTERN LOOKS LIKE A CLASSIC MID-WINTER WEDGE DESPITE
TEMPERATURES A GOOD 25-30 DEGREES WARMER. STILL...HIGHS IN THE UPPER
60S TO LOWER 70S IN SEPTEMBER ARE NOTHING TO SNEEZE AT. THE GFS MOS
LOOKS CLOSER TO REALITY THAN THE NAM...BUT EVEN IT IS PROBABLY A
LITTLE TOO WARM IN MOST AREAS.

AFTER A RELATIVE LULL IN PRECIPITATION COVERAGE LATE THIS AFTERNOON
AND THIS EVENING...SUBSTANTIAL RAINFALL MAY AGAIN SURGE ONTO THE
COAST OVERNIGHT AS STRONGER LOW-LEVEL WIND FIELDS DEVELOP AND
ISENTROPIC LIFT INCREASES. PRECIP SHOULDN`T PENETRATE QUITE AS FAR
INLAND HOWEVER DUE TO A MORE BACKED/NORTHERLY LOW-LEVEL WIND
DIRECTION...AND MY FORECAST POPS RANGE FROM 60-80 PERCENT ON THE
COAST TO 20-30 PERCENT ALONG THE I-95 CORRIDOR. UNDER CLOUDS AND A
STIFF NORTHEAST WIND LOWS SHOULD FALL INTO THE UPPER 50S INLAND AND
LOWER 60S NEAR THE COAST.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUESDAY...VERY UNSETTLED DURING THE SHORT TERM AS A
STAGNANT PATTERN CONTINUES ACROSS THE CONUS. ALOFT...AN UPPER LEVEL
LOW CLOSED OFF ACROSS SC WILL ONLY SLOWLY FILL AND LIFT...LIKELY
MAINTAINING AT LEAST SOME SEMBLANCE OF AN UPPER TROUGH THROUGH
THURSDAY NIGHT. THIS IS DUE TO A HIGHLY AMPLIFIED RIDGE ACROSS THE
ATLANTIC...AS WELL AS GROWING RIDGING ACROSS THE CENTER PART OF THE
COUNTRY FORCING SYSTEMS TO GRIND TO A HALT. AT THE SURFACE...A VERY
STRONG 1035+ MB SURFACE HIGH WILL WEDGE DOWN FROM NEW ENGLAND WHILE
A COASTAL TROUGH SHARPENS AND LURKS OFFSHORE...ALONG WITH VERY
STRONG MOIST ADVECTION.

THESE FEATURES TOGETHER WILL CREATE AN EXTENDED PERIOD OF COOL TEMPS
WITH WIDESPREAD SHOWERS AND CLOUDS...AS WELL AS GUSTY NE WINDS.
WHILE THERE IS STILL CONSIDERABLE SPREAD AMONG THE VARIOUS GUIDANCE
INTO HOW FAR WESTWARD THE COASTAL TROUGH WILL LIFT...AND THUS HOW
HEAVY THE RAIN WILL BE...IT SEEMS ALMOST CERTAIN THAT THE COAST WILL
SEE RAIN DURING THIS PERIOD...WITH A SHARP GRADIENT TOWARDS I-95.
THE INTERACTION OF THE UPPER LOW WITH THE COASTAL TROUGH WILL
SHARPEN THE TROUGH ON WEDNESDAY...AND MAY EVEN SPAWN A WEAK LOW
MOVING JUST ALONG THE COAST INTO THURSDAY. THIS COMBINED WITH DEEP
MOIST ADVECTION ON EASTERLY FLOW...DRIVING INCREASING ISENTROPIC
LIFT ATOP THE COASTAL BOUNDARY...SUGGESTS AT LEAST PERIODS OF HEAVY
RAIN POSSIBLE ALONG THE IMMEDIATE COAST WEDNESDAY...DECREASING
SOMEWHAT INTO THURSDAY. AGAIN...HOW FAR INLAND THE RAIN WILL
PENETRATE IS STILL UNCERTAIN...BUT THE HEAVIEST RAIN AND HIGHEST POP
WILL CERTAINLY BE RIGHT ALONG THE IMMEDIATE COAST.

TEMPS BOTH WED AND THU WILL STAY WELL BELOW CLIMO WITH HIGHS ONLY IN
THE LOW/MID 70S...MADE TO FEEL EVEN MORE RAW BY NE WINDS AND RAIN.
LOWS AT NIGHT HOWEVER WILL BE SOMEWHAT HELD IN CHECK BY THE SAME
CLOUDS AND RAIN...SO EVEN WITH COOL NE WINDS PERSISTING
OVERNIGHT...MINS WILL BE JUST ABOVE CLIMO IN THE LOW/MID 60S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...THE EXTENDED BEGINS COOL AND
UNSETTLED...MAYBE UNSURPRISINGLY BY THIS POINT...AS THE PERSISTENT
COASTAL TROUGH REMAINS JUST OFFSHORE WHILE HIGH PRESSURE REORGANIZES
ACROSS THE GREAT LAKES. LOW PRESSURE ALONG THE OFFSHORE BOUNDARY
MOVING NEAR NEW ENGLAND WILL PUSH NORTHEAST AWAY FROM THE AREA BY
SATURDAY...WHICH IN CONJUNCTION WITH THE EXPANSION OF THE MIDWEST
HIGH WILL DRIVE THE OFFSHORE BOUNDARY WELL EAST BY THE WKND.
ALOFT...THE QUASI-STATIONARY TROUGH WILL FILL AS RIDGING BLOSSOMS
ACROSS THE MIDDLE OF THE COUNTRY...BEFORE PUSHING OVERHEAD DURING
THE WKND. THESE FEATURES COMBINED SUGGEST A DRYING
TREND...ESPECIALLY FROM SATURDAY INTO MONDAY...ALONG WITH TEMPS
WARMING TO SEASONABLE OR ABOVE...AND THE FIRST WKND OF FALL WILL
FEATURE PLEASANT WEATHER ACROSS THE AREA.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
AS OF 06Z...LIGHT STRATIFORM RAIN ACROSS CENTRAL SOUTH CAROLINA IS
SPREADING SLOWLY EASTWARD. MODELS INDICATE A SECOND AREA OF RAIN
WITH EMBEDDED CONVECTIVE ELEMENTS WILL DEVELOP OFFSHORE BEFORE
DAYBREAK...SPREADING ONSHORE 11-13Z.

CEILINGS CURRENTLY 6KFT-10KFT SHOULD LOWER TOWARD SUNRISE...BUT
SHOULD NOT BECOME IFR UNTIL 14Z AS MORE SUBSTANTIAL RAINFALL RATES
DEVELOP NEAR THE COAST. INCREASING N-NE WINDS EXPECTED AFTER
DAYBREAK WITH GENERALLY MVFR CONDITIONS...POSSIBLY VFR AT THE INLAND
TERMINALS DURING THE AFTERNOON.

EXTENDED OUTLOOK...UNSETTLED WEATHER THROUGH THE PERIOD...MAINLY AT
THE COASTAL TERMINALS WITH PERIODS OF RAIN/SHOWERS AND INTERMITTENT
MVFR/IFR CONDITIONS.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM TUESDAY...THIS MORNING`S SUITE OF MODEL RUNS HAVE
UNFORTUNATELY ALL TRENDED TOWARD STRONGER WIND SPEEDS AND HIGHER
SEAS DEVELOPING OVER THE NEXT 24 HOURS. A STALLED FRONT OUT OVER
THE GULF STREAM WILL DEVELOP A WAVE OF LOW PRESSURE ALONG IT
TONIGHT ALONG THE GEORGIA AND SOUTH CAROLINA COAST. CANADIAN HIGH
PRESSURE WILL ALSO TRY TO RIDGE SOUTHWARD FROM NEW ENGLAND. THIS
WILL PINCH THE PRESSURE GRADIENT RATHER SIGNIFICANTLY ALONG THE
CAROLINA COAST...WITH DETERIORATING WEATHER CONDITIONS THE RESULT.

WINDS CURRENTLY ARE NORTHERLY AT 10-15 KNOTS. SHORTLY AFTER DAYBREAK
A SURGE OF 20 KNOT NORTHEASTERLY WINDS SHOULD MOVE DOWN THE COAST...
WITH 25 KNOT WINDS DEVELOPING THIS AFTERNOON. THE WORST CONDITIONS
ARE EXPECTED TO OCCUR TONIGHT WHEN WINDS COULD REACH 30 KNOTS. ONE
CONCERN IS THE NORMALLY QUITE RELIABLE GFS MODEL IS SHOWING WINDS
JUST 1000 FEET ALOFT ACCELERATING TO 35 KNOTS OVERNIGHT ALONG THE
SOUTH CAROLINA COAST. DEPENDING ON HOW MUCH HEAT FROM THE WARM OCEAN
SURFACE CAN WARM THE AIRMASS...WE COULD CONCEIVABLY SEE THESE
GALE-FORCE WINDS COME DOWN TO THE SURFACE AT LEAST IN GUSTS. SEAS
CURRENTLY ONLY 2-3 FEET SHOULD BUILD STEADILY IN RESPONSE TO THE
WINDS...REACHING AS HIGH AS 6-8 FEET TONIGHT.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUESDAY...HIGH PRESSURE WILL WEDGE DOWN THE COAST
THROUGH THE SHORT TERM...WHILE A COASTAL TROUGH REMAINS JUST
OFFSHORE THE CAROLINAS. THIS WILL PRODUCE CONSISTENT NE WINDS
THROUGH THE PERIOD...WITH THE HIGHEST SPEEDS OCCURRING ON WEDNESDAY
AS A WAVE OF LOW PRESSURE MOVES ALONG THE TROUGH...PINCHING THE
GRADIENT. NE WINDS MAY EXCEED 25 KTS THE FIRST HALF OF
WEDNESDAY...WITH GUSTS APPROACHING GALE FORCE. THESE WINDS WILL EASE
SLOWLY WED NIGHT AND THE FIRST PART OF THURSDAY...BECOMING 15-20
KTS...BEFORE SLOWLY RAMPING UPWARD AGAIN THURSDAY NIGHT. THESE WINDS
WILL KEEP WAVE AMPLITUDES ELEVATED...4-7 FT EXPECTED WED AND THU.
THERE MAY BE A BRIEF PERIOD WED NIGHT INTO THURSDAY WHEN WAVE
HEIGHTS DROP BELOW SCA THRESHOLDS...BUT EVEN SO...EXPECT HEADLINES
TO BE IN EFFECT THE ENTIRETY OF THE PERIOD.

LONG TERM /FRIDAY THROUGH SATURDAY/...
AS OF 300 AM TUESDAY..HIGH PRESSURE WILL SOMEWHAT RE-ORIENT ITSELF
INTO THE WKND...BECOMING CENTERED ACROSS THE GREAT LAKES INSTEAD
OF NEW ENGLAND. WHILE THIS LEAVES A WEDGE IN PLACE LOCALLY...IT
WILL BE OF DECREASED STRENGTH...AND THUS NE WINDS WILL BE SOMEWHAT
LOWER THAN EARLIER IN THE WEEK...15-20 KTS INTO THE WKND. A SMALL
CRAFT ADVISORY WILL LIKELY BE NEEDED FOR AT LEAST A PORTION OF THE
EXTENDED...LIKELY MOST OF FRIDAY...FOR 4-6 FT SEAS...BEFORE
AMPLITUDES WANE ON SATURDAY.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT WEDNESDAY FOR
     AMZ250-252-254-256.

&&

$$
SYNOPSIS...JDW
NEAR TERM...TRA
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...TRA
MARINE...TRA/JDW








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